Availability and accumulation of lead for forage grasses in contaminated soil

Abstract

The forage grasses are explored for the phytoremediation of heavy metals from contaminated areas. The present study evaluates the tolerance of forages grasses to Pb and the availability of Pb for the Mehlich 1, DTPA, and USEPA 3051 and 3052 extraction methods. The forage grasses cultivars Panicum maximum cultivars Aruana and Tanzânia, Brachiaria decumbens cultivar Basilisk, Brachiaria brizantha cultivar Xaraés and Marandu were assessed. Each cultivar was grown in a greenhouse in Diamantina, Brazil, in Typic Hapludox (Oxisol). The Pb was applied to the soil at doses of 0, 45, 90 and 270 mg kg-1 soil in a randomized design with four replications. The experiment was conducted over a 90-day trial period. Increasing Pb doses in the soil caused a reduction of growth in all varieties studied, and the "Basilisk" forage was generally more tolerant to Pb, while the Xaraés forage was generally more susceptible to the addition of Pb. The lower transfer coefficient of the cultivar "Basilisk", due to the high Pb content and accumulation in its roots, makes it the most suitable for phytoremediation programs, with possible uses in pasture areas. None of the varieties can be considered a Pb hyperaccumulator. The Mehlich 1, DTPA, USEPA 3051 and USEPA 3052 extraction methods indicated different doses of Pb in the soil, and the Mehlich 1 method demonstrated the lowest level of metal extraction from the soil. No correlation was observed between the forage grasses growth and the measurement of Pb in soil by the studied extraction methods, especially for the Mehlich 1 and DTPA methods, suggesting the inefficiency of these techniques for determining the phytoavailability of Pb.

Induced changes in the growth of four plant species due to lead toxicity

“…The highest Pb contents in the roots of the evaluated species were similar to those found by Nascimento et al (2014), who studied Pb accumulation in forage species in contaminated soils. The accumulation of Pb in the roots has been attributed to its low mobility in the plant, high affinity for the negative charges of the cell wall and to the physiological barriers of Casparian strips, which restrict its access to the xylem, reducing the translocation (Zhivotovsky et al, 2011).…”

Growth of tropical grasses in Oxisol contaminated by nickel

“…The United States Environmental Protection Agency recommends determining the pseudo total present in the sample concentration (USEPA, 2007) to monitor soil pollution by heavy metals. Conventionally, this analysis requires digestion with hydrofluoric acid (HF) together with other strong acids (Nascimento et al, 2014). However, the use of HF in routine laboratories is not recommended because this reagent is difficult to handle.…”

Potássio na amenização dos efeitos tóxicos induzidos pelo cádmio no capim tanzânia

“…Nos anos recentes, o capim tanzânia tem sido estudado sob condições de fitotoxicidade e em recuperação de áreas contaminadas por metais pesados (Miranda et al 2012;Monteiro et al 2011;Nascimento et al 2014;Silva et al 2016). A contaminação dos solos por metais pesados é importante problema ambiental devido aos danos causados na qualidade do solo e as graves consequências na saúde animal e humana.…”

“…A contaminação dos solos por metais pesados é importante problema ambiental devido aos danos causados na qualidade do solo e as graves consequências na saúde animal e humana. Uma das estratégias para mitigar o problema é o uso de uma tecnologia ambientalmente correta e de baixo custo, a fitorremediação (Nascimento et al 2014;.…”

“…Na fitoextração, o contaminante é absorvido pelas raízes e transportado para a parte aérea, tornando possível sua remoção do solo por meio do corte e retirada do material colhido . O capim tanzânia apresenta potencial para ser empregado nessas duas técnicas (Monteiro et al 2011;Nascimento et al 2014;Silva et al 2016;Souza Júnior et al 2018).…”